2(4-n-Hexadecyl amino or oxy phenyl) 5 ethoxy oxazoleacetic acid derivatives

ABSTRACT

Oxazoleacetic acid derivatives of the formula ##STR1## and salts thereof wherein R 1  is a higher alkyl group having 10 to 20 carbon atoms, a higher alkenyl group, a benzyl group or a halogen substituted benzyl group; X is O, S or NH; R 2  is a lower alkyl group, a phenyl group or a halogen-substituted phenyl group and R 3  is a hydrogen atom or a lower alkyl group, having a hypolipidemic activity.

TECHNICAL FIELD AND DISCLOSURE OF THE INVENTION

This invention relates to novel and therapeutically valuableoxazoleacetic acid derivatives of the formula ##STR2## and saltsthereof, wherein: R is a higher alkyl group having 10 to 20 carbon atoms(e.g. decyl, dodecyl, tetradecyl, hexadecyl or octadecyl), a higheralkenyl group (e.g. decenyl, dodecenyl, tetradecenyl, hexadecenyl oroctadecenyl), a benzyl group or a halogen(fluorine, chlorine, bromine oriodine)-substituted benzyl group; X is O, S or NH; R² is a lower alkylgroup (e.g. methyl, ethyl, propyl or butyl), a phenyl group or ahalogen-substituted phenyl group; and R³ is a hydrogen atom or a loweralkyl group.

Examples of the salts of compounds of the formula (I) are inorganicsalts, e.g. sodium salts, magnesium salts, calcium salts, aluminumsalts, ammonium salts; amine salts, e.g. dimethyl amine salts; trimethylamine salts; or amino acid salts, e.g. arginine salts, lysine salts.

The compounds of the formula (I) can be prepared according to one of thefollowing methods (1) to (3):

METHOD (1)

In the case of compounds of formula (I) wherein R³ is a lower alkylgroup, by dehydrating for ring-closure a compound of the formula##STR3## wherein R¹, X and R² are as defined above and R⁴ is a loweralkyl group.

The reaction is carried out by treating the compound of formula (II)with a dehydrating agent such as phosphorus pentoxide, phosphoruspentachloride, phosphorus oxychloride, thionyl chloride, tosyl chlorideor concentrated sulfuric acid, at room temperature or under heating,optionally in a solvent such as benzene, toluene, chloroform or1,2-dichloroethane. In the case of compounds of formula (II) wherein Xis NH, the compound is preferably protected with an amino-protectinggroup (e.g. formyl, trifluoroacetyl, tosyl, benzyloxycarbonyl orphthalyl), and then subjected to dehydration for ring closure and toremoval of the protecting group.

The starting compounds of formula (II) can be prepared in a conventionalmanner from aspartic acid which may have L-, D- or DL-configuration.

METHOD (2)

In the case of compounds of formula (I) wherein R³ is a hydrogen atom,by hydrolyzing a compound of formula (I) wherein R³ is a lower alkylgroup.

The hydrolysis may be carried out with an acid or an alkali, preferablywith a diluted alkali solution (e.g. sodium hydroxide or potassiumhydroxide) in water, a water-soluble organic solvent (e.g. methanol,ethanol, acetone, dioxan or tetrahydrofuran) or a mixture thereof.

METHOD (3)

In the case of compounds of formula (I) wherein R³ is a lower alkylgroup, by reacting a compound of formula (I) wherein R³ is a hydrogenatom (a carboxylic acid) or a functional derivative thereof [e.g. anacid chloride, an acid anhydride, an acid azide, or a reactive ester(e.g. p-nitrophenyl ester or N-hydroxysuccinimide ester)] with a loweralkanol.

The oxazoleacetic acid derivatives and salts thereof of this inventionpossess an excellent hypolipidemic activity and very low toxicity, asshown by the following experiments, and are useful as drugs for thetreatment of atherosclerosis with lipid metabolism disorder orintermediates therefor.

EXPERIMENTS

(1) Test Compounds

Compound A: 2-(4-n-Hexadecyloxyphenyl)-5-ethoxy-4-oxazoleacetic acid

Compound B: Sodium2-(4-n-hexadecylaminophenyl)-5-ethoxy-4-oxazoleacetate

Compound C:2-(4-n-Hexadecyloxyphenyl)-5-(4-chlorophenoxy)-4-oxazoleacetic acid

Compound D: 2-[4-(4-Chlorobenzyloxy)phenyl]-5-ethoxy-4-oxazoleaceticacid

Compound E: Clofibrate (for comparison)

(2) Test methods and results:

(i) Male Sprague-Dowley rats were used. Each group was composed of 8animals. Rats were fed a diet containing 1% of cholesterol. The testcompound was orally administered to the animal by feeding with the dietto which the compound was blended in a ratio of 0.1% (W/W) for 5 days.Cholesterol and triglyceride in the serum were determined by thestandard methods using an autoanalyzer (Technicon Inc.). The levels inthe control group were considered as 100% and the reduction rate in thetest group was calculated. The results are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                        Test          Reduction Rate (%)                                              Compound      Cholesterol                                                                             Triglyceride                                          ______________________________________                                        A             21        35                                                    B             31        28                                                    C             31        37                                                    D             37        42                                                    E             22        23                                                    ______________________________________                                    

(ii) With the exception that rats were fed a conventional diet insteadof the diet containing 1% cholesterol, a test was carried out in thesame condition (rats used, administration method, period, concentrationof test compound and cholesterol and triglyceride determination) as inthe above test (i). The reduction rates thus obtained are shown in Table2.

                  TABLE 2                                                         ______________________________________                                        Test          Reduction Rate (%)                                              Compound      Cholesterol                                                                             Triglyceride                                          ______________________________________                                        A             29        44                                                    B             26        44                                                    D             19        53                                                    E             23        34                                                    ______________________________________                                    

(iii) Male dd-strain mice were used. Each group was composed of 10animals. The test compound was administered intraperitoneally or orallyto the animals. The LD₅₀ (mg/kg) was calculated from the mortalitywithin 7 days after administration of the test compound. The results aregiven in Table 3.

                  TABLE 3                                                         ______________________________________                                                   LD.sub.50                                                          Test         Intraperitoneal                                                                           Oral                                                 Compound     administration                                                                            administration                                       ______________________________________                                        A            >1,000 mg/kg                                                                              >2,500 mg/kg                                         B            >1,000 mg/kg                                                                              >2,500 mg/kg                                         E            >1,000 mg/kg                                                                              >1,450 mg/kg                                         ______________________________________                                    

(iv) Rhesus monkeys having hyperlipemia fed with a diet containing 0.25%cholesterol were used. A diet containing 0.7% (W/W) of the test compoundA or B was administered for 15 days. An outstanding reduction activityof blood cholesterol was observed in the administered group as comparedwith the control group.

In view of various standpoints including the above-mentionedexperiments, the compounds (I) and salts thereof of the presentinvention can be administered safely as drugs for the treatment ofatherosclerosis with lipid metabolism disorder, in the form of aphamaceutical preparation with a suitable and conventional carrier oradjuvant which is administered orally without harmful side effects tothe patients.

The oral daily dose of the compounds of the present invention for humanadults usually ranges from 100 to 1,000 mg.

FORMULATION EXAMPLE

Tablets of 200 mg are prepared from the following compositions:

    ______________________________________                                        Compound A              200.0  mg                                             Lactose                 35.5   mg                                             Microcrystalline cellulose                                                                            10.0   mg                                             Starch                  30.0   mg                                             Talc                    3.5    mg                                             Magnesium stearate      1.0    mg                                                                     280.0  mg                                             ______________________________________                                    

REFERENCE EXAMPLE [Preparation of the starting compounds (II)] DiethylN-4(n-hexadecyloxy)benzoyl-L-aspartate

To a solution of 16 g of 4-(n-hexadecyloxy)benzoyl chloride and 9.4 g ofdiethyl L-aspartate in 140 ml of tetrahydrofuran under ice-cooling wasadded dropwise 5.0 g of triethylamine with stirring. After stirringunder ice-cooling for 90 minutes, the insoluble substances were filteredoff. To the filtrate were added ice and ethyl acetate. The organic layerwas successively washed with diluted hydrochloric acid, diluted sodiumbicarbonate solution and water, dried over anhydrous sodium sulfate, andthen concentrated under reduced pressure. The residue was recrystallizedfrom hexane to give 20.3 g of the title compound as white crystals, m.p.68°-69° C.

The following compound can be prepared in a similar manner as above.

Diethyl N-4-(4-chlorobenzyloxy)benzoyl-L-aspartate, m.p. 91.5°-93° C.

EXAMPLE 1 (a) Ethyl 2-(4-n-hexadecyloxyphenyl)-5-ethoxy-4-oxazoleacetate

To a solution of 20.3 g of diethylN-4-(n-hexadecyloxy)benzoyl-L-aspartate in 150 ml of toluene was added10 ml of phosphorus oxychloride. The resulting solution was refluxedunder heating for 75 minutes. After cooling, the solution was pouredinto a mixture of ice and potassium carbonate. After stirring for awhile, to the resulting solution was added ethyl acetate and the wholesolution was shaped to separate an organic layer. The organic layer waswashed with water, dried over anhydrous sodium sulfate and concentratedunder reduced pressure. The residue was recrystallized from hexane togive 20 g of the title compound, m.p. 44°-45° C.

(b) 2-(4-n-Hexadecyloxyphenyl)-5-ethoxy-4-oxazoleacetic acid

To a solution of 20 g of ethyl2-(4-hexadecyloxyphenyl)-5-ethoxy-4-oxazoleacetate in 200 ml of methanolwas added a solution of 7.6 g of sodium hydroxide in 20 ml of waterunder stirring at room temperature and stirred for about 3.5 hours. Thereaction mixture was concentrated under reduced pressure. The residuewas dissolved in water and the solution was acidified with hydrochloricacid to pH 1 under cooling. The precipitate was filtered off, dried andrecrystallized from methanol to give 11.7 g of the title compound ofwhite powder, m.p. 89°-91° C.

The following compounds can be prepared in the same manner as in (a).

Ethyl 2-[4-(4-chlorobenzyloxy)phenyl]-5-ethoxy-4-oxazoleacetate, m.p.96°-97.5° C.

Ethyl 2-(4-n-dodecyloxyphenyl)-5-ethoxy-4-oxazoleacetate, m.p.48.5°-49.5° C.

Ethyl 2-(4-n-tetradecyloxyphenyl)-5-ethoxy-4-oxazoleacetate, m.p.41.5°-42.5° C.

Ethyl 2-(4-n-octadecyloxyphenyl)-5-ethoxy-4-oxazoleacetate, m.p. 54° C.

Ethyl 2-(4-n-hexadecylthiophenyl)-5-ethoxy-4-oxazoleacetate

The following compounds can be prepared in the same manner as in (b):

2-[4-(4-Chlorobenzyloxy)phenyl]-5-ethoxy-4-oxazoleacetic acid, m.p.130°-131° C.

2-(4-n-Dodecyloxyphenyl)-5-ethoxy-4-oxazoleacetic acid, m.p. 86°-87° C.

2-(4-n-Tetradecyloxyphenyl)-5-ethoxy-4-oxazoleacetic acid, m.p.88.5°-89° C.

2-(4-n-Octadecyloxyphenyl)-5-ethoxy-4-oxazoleacetic acid, m.p. 77°-78°C.

2-(4-n-Hexadecylthiophenyl)-5-ethoxy-4-oxazoleacetic acid

EXAMPLE 2 Sodium 2-(4-n-hexadecylaminophenyl)-5-ethoxy-4-oxazoleacetate

To a suspension of 46.5 g of 4-(n-hexadecylamino)benzoic acid in 300 mlof pyridine was dropwise added trifluoroacetic anhydride with stirringunder ice-cooling in the course of 15 minutes. After the mixture wasfurther stirred at room temperature for 90 minutes, the mixture waspoured into ice-water and extracted with ethyl acetate. The organiclayer was successively washed with diluted hydrochloric acid and water,dried over anhydrous sodium sulfate and concentrated. To the residualoily N-trifluoroacetyl derivative, without purification, were added 100ml of thionyl chloride and 300 ml of benzene. The whole mixture wasrefluxed under heating for 110 minutes and completely concentrated. Theresidue was reacted and treated with 29.2 g of diethyl L-aspartate inthe same manner as described in reference example to give 73 g ofdiethyl N-[4-(N-trifluoroacetyl-N-n-hexadecylamino)benzoyl]-L-aspartate.To a solution of the oil in 500 ml of toluene was added 40 ml ofphosphorus oxychloride. After the mixture was refluxed under heating for120 minutes, the resulting solution was poured into a mixture of ice andpotassium carbonate and then extracted with benzene. The benzene layerwas further washed with diluted aqueous potassium carbonate solution andaqueous sodium chloride solution, dried over anhydrous sodium sulfateand concentrated under reduced pressure. The residue obtained, withoutpurification, was dissolved in 300 ml of methanol. To the solution wasadded a solution of 14 g of sodium hydroxide in 80 ml of water at roomtemperature and the whole solution was stirred for 60 minutes. Theresulting solution was concentrated under reduced pressure. To theresidue was added cold water and the precipitated solid was filteredoff. The precipitate was dissolved into ethanol under heating, andactive carbon was added to the solution. The mixture was filtered togive 25.9 g of the title compound, m.p. 188.5°-198.5° C.

EXAMPLE 3 2-(4-n-Hexadecyloxyphenyl)-5-(4-chlorophenoxy)-4-oxazoleaceticacid

To a solution of 19 g of 4-(n-hexadecyloxy)benzoyl chloride and 11.9 gof β-ethyl L-aspartate hydrochloride in 200 ml of tetrahydrofuran withstirring under ice-cooling was dropwise added 55 ml of triethylamine.With further stirring for 130 minutes, the reaction mixture was pouredinto diluted hydrochloric acid and the mixture was extracted with ethylacetate. The organic layer was washed with water, dried anhydrous sodiumsulfate and concentrated under reduced pressure. A part of residualβ-ethyl N-(4-n-hexadecyloxybenzoyl)-L-aspartate (a white solid, 18.1 g)which is not purified was dissolved into 200 ml of ethyl acetate. To theresulting solution were added 9.2 g of p-chlorophenol and 7.4 g ofdichlorohexylcarbodiimide and the mixture was stirred at roomtemperature for 60 minutes. The precipitated dicyclohexylurea wasfiltered off. The filtrate was concentrated and the residue was vacuumdistilled.

After removing the forerun (excess p-chlorophenol) only, the residue wasdissolved in 100 ml of toluene. With addition of 15 ml of phosphorusoxychloride, the solution was refluxed under heating for 210 minutes.After cooling, the mixture was poured into a mixture of ice andpotassium carbonate for decomposition and the mixture was extracted withethyl acetate. The organic layer was washed with water, dried overanhydrous sodium sulfate and concentrated under reduced pressure. Theresidue obtained was dissolved in 100 ml of acetone. To the solution wasadded an aqueous solution of 3.0 g of sodium hydroxide and the solutionwas stirred at room temperature for 30 minutes. The resulting mixturewas concentrated under reduced pressure. After addition of ice-water,the residue was acidified with hydrochloric acid. The separated solidwas filtered off, dried and recrystallized from methanol. The crystalsthus obtained were filtered off and further recrystallized from hexaneto give 6 g of the title compound as a white fine powder, m.p. 76°-77°C.

The following compounds can be prepared in the same manner as in theabove example.

2-[4-n-(9-Octadecenyl)oxyphenyl]-5-ethoxy-4-oxazoleacetic acid, m.p.75.5°-76.5° C.

2-[4-(4-Chlorobenzylamino)phenyl]-5-ethoxy-4-oxazoleacetic acid

2-[4-(4-Chlorobenzylthio)phenyl]-5-phenoxy-4-oxazoleacetic acid

While the invention has been explained in detail with references to theabove description and examples included therein, various alterations andmodifications can apparently be made without departing from the spiritand scope of the invention.

We claim:
 1. Ethyl 2-(4-n-hexadecyloxyphenyl)-5-ethoxy-oxazoleacetate.2. 2-(4-n-Hexadecyloxyphenyl)-5-ethoxy-4-oxazoleacetic acid.
 3. Sodium2-(4-n-hexadecylaminophenyl)-5-ethoxy-4-oxazoleacetate.